A touch sensor is known as an interface allowing a user to input information to a display device. The touch sensor is set on a screen of the display device, so that the user may operate an input button, an icon or the like displayed on the screen to easily input information to the display device. For example, United States Patent Application Publication No. 2015/0185942 discloses an electronic device including a touch sensor provided in an organic EL (electroluminescence) display device.
A conventional display device including a touch sensor described in United States Patent Application Publication No. 2015/0185942 requires an electrode for the touch sensor to be provided in addition to a conductive layer included in the display device. Especially, in the case where an electrostatic capacitance-type touch sensor is used, a pair of electrodes need to be additionally provided in the display device in order to form a capacitance element that detects the touch of the user. Therefore, in order to incorporate a touch sensor in the display device, at least two conductive layers need to be provided in addition to the conductive layer conventionally provided in the display device.